This disclosure is directed generally to butterfly valves, and more specifically, to pistons used for actuation of butterfly valves.
Pneumatically actuated butterfly valves require a means for converting the axial motion of the piston into rotary motion to control the position of the valve disc which is used to modulate a primary air flow. Typically a link with bearings at each end provides the connection between the piston and the crank arm which rotates the shaft for the butterfly disc. Often there are wear issues associated with the bearings at either end of the crank. Also, in high vibration environments like engine bleed systems, a piston torsional mode may be excited which leads to excessive piston ring wear. In such arrangements, the piston has the rotational inertia and the link provides the torsional stiffness.